Apple posted a support document over the weekend on its Web site addressing reports of interminable "blue screen" problems that caused some Mac users upgrading to Mac OS X Leopard no small degree of frustration.
Some attempts to upgrade to Leopard were stymied after the installation process was almost complete and users attempted to restart their machines. A long thread on Apple's discussion forums outlined the problems, in which their Macs would get hung up on the initial boot screen. That screen happens to be blue, inviting comparisons to the infamous Windows "blue screen of death" encountered when Windows crashes.
Apple said the problem could be related to "application enhancement software," and a Computerworld article identified Unsanity's APE software as the source of many complaints. Unsanity develops software that allows Mac users to customize the look and feel of Mac OS. An Unsanity representative told Computerworld that problems might occur only on outdated versions of APE that shipped before Apple switched to Intel's chips.
Problems were also noted in Apple's support forums by Mac users who had never installed the APE software, however, so it doesn't appear that all the blame can be placed on third-party enhancement software. Apple recommended two solutions for Leopard owners attempting to upgrade: novice users should reinstall Leopard using the "Archive and Install" method detailed here. Mac owners who have been around the block a few times can try the other solution, which involves using the command line to get rid of the application enhancement software.
If you've tried those suggestions and you're still having trouble completing the upgrade, check out the discussions forum on Apple's support page, and let us know what's going on.